A variety of power converters are used throughout industry. Power converters are often utilized in electronic circuits for direct current (DC) or alternate current (AC) conversion to supply power to electric motors. Such conversion is performed on hybrid electric vehicles, fan drives, washing machines, refrigerators, and other various machines and equipment to improve efficiency and performance, as well as to minimize noise.
Certain electronic circuits exhibit high switching speeds. At high switching speed, the electronic circuits generate common-mode (CM) and differential-mode (DM) electromagnetic interference (EMI) noises. Thus, CM and DM filters are incorporated to remove such noise. The theoretically simplest filter topologies include capacitors and inductors that are without mutual-couplings between windings. However, in actual implementation, the inductors are normally with mutually coupled windings to minimize inductor size. Depending on the coupling polarity to the inductors and the number of inductors used, the CM or DM noises can be effectively blocked. Traditionally, a first inductor is used to filter CM noises and a second inductor is used to filter DM noises. A single traditional inductor is not effective in simultaneously filtering both CM and DM noises, due to the structure thereof.
There is a desire to further reduce the circuit size, cost, complexity, and weight associated with CM and DM inductor filtering. Thus, there is a need for an improved technique of providing CM and DM inductor filtering.